Hermetically-sealed electric switch



1. E. MCCABE ET AL 1,705,989

H ERMETICALLY SEALED ELECTRIC SWITCH March 19; 1929..

Filed April 14, 1926 (IIINu- IN VEN TOR 9M Wr/k v ATTORNEY Patented Mar.19, 1929.

UNITED STATES PATENT OFFICE.

IRA E. MoGAIBE, OF CHICAGO, AND RAYMOND W. ARMSTRONG, OI WILMETTEi,ILLI- NOIS; SAID ARMSTRONG ASSIGNOR OF HIS RIGHT FANY, A CORPORATION OFILLINOIS.

TO THE ARCLESS CONTACT CO1!- HERIETIGALLYQEALED ELECTRIC SWITCH.

Application filed April 14, 1926. Serial No. 101,887.

The present invention relates particularly to so-called mercury switchesin which there is a body of mercury in a sealed receptacle through awall of which extend leading-1n 5 wires terminating in contacts orelectrodes that are adapted, in one position of the receptacle, to beengaged with'the mercury so as electrically .to connect them together;

while, in another position of the receptacle,

the mercury is carried away from one or both of the electrodes orcontacts, interrupting the connection between the same.

In the present, highly developed type of mercury switch the receptacleis made of glass that is hermetically sealed, the leading-in wires arehermetically sealed in a wall of the receptacle, and the electrodes andthe gaseous content of the receptacle are so chosen that there ispractically no deterioration through lapse of time or long and severeuse. The leading-in wires must be made of. a material that has the samecoeflicient of expansion as the glass; so that the joints between thewires and the glass will not be broken because of unequal expansionastemperature changes occur. The electrodes, on the other hand, must bemade of a material that will not be acted upon chemically by themercury, and such material may have an entirely difierent coefficient ofexpansion than that of glass. In the ordinary commercial switches theleading- 1n wires are special copperclad wires, while the electrodes aremade of iron. In the manufacture of these switches, because the iron hasa different coefficient of expansion than has glass, it has beennecessary to take great pains so to place the joint between a leading-inwire and-its electrode, that the difference between the coeflicients ofex ansion of iron and glass would not bring a out a break in the seal,under temperature changes while, at the same time, the leadingin wireswould be fully shielded against contact with. the mercury. Perfectlymade switches of this kind have therefore been expensive. A

The object of the present inventlon is to produce a simple and novelconstruction and arrangement that will permit mercury switches to becompleted, to the extent of placing in position the electrodes and lead-1ng-1n wires and forming the seal around the leading-in wires byautomatic mach nery, and thus greatly reduce their cost of manufacture,by reducing the need for the extreme accuracy that it has heretoforebeen necessary to practice in locating a oint between a leading-in wireand an electrode, with respect to the.glass through which the leading-inwire passes;

The various features of novelty whereby the invention is characterizedwill hereinafter he pointed out with particularity in the claims; but,for a full understanding of our invention and of its objects andadvantages, reference may be'had to the following detailed descriptiontaken in connection with the accompanying drawing, wherein:

Figure 1 is a side elevation of a switch arranged in accordance with thepresent invention, having short terminal conductors connected thereto;Fig. 2 is a view looking at the top of .the device as it appears in Fig.1'; Fig. 3 is a side view, similar to Fig. 1, on a larger scale, asection of the switch being broken away Fig. 4 is a topplan view of theswitch on the same scale as Fig. '3; and Figs. 5 and 6 are views similarto Figs. 3 and 4 showing another embodiment an of the presentinvention'.

Referring to Figures 1-4 of the drawings, 1 represents a glassreceptacle that may conveniently be made from a piece of glass tubingclosed 'at the ends; Within the reas ceptacle is a small body of mercury2. 3 and 4 are electrodes of iron or other suitable material in the formof eyelets; theseeyelets having stems that are oined to leading in wires5 and 6. In assembling the leadingin wires and electrodes in the,switch, one 'end of the glass tube is heated; the elw trodes attached tothe leading-in wires are inserted in the heated end of the tube with.the eyelets arranged parallel with each other; and the heated end ofthe tube is then flattened by applying pressure on opposite sides in adirection at right angles to a plane containing the leading-in wlresthus forming a flattened neck 7 The leadlng-in wires, during theflattening of the end of the tube, are held in such a position that theflattened area will. be certain to extend joints between the electrodesand the leading-- in wires. The electrodes need not be positioned withextreme accuracy, as it is not important whether the length of the stemsof an electrode that is sealed into the glass varies a few hundredths ofan inch.

There are several reasons why in the construction just described therewill be no injury tothe seal on account of a difference between thecoefficients of expansion of the glass and of the material of which theelectrodes are made. The leading-in wires of the electrodes are small-indiameter and are spaced apart along the long dimension of the crosssection of the flattened neck of the tube, so that any plane parallel tothe short dimension of this neck goes through only a single I wire; andtherefore the glass is strong enough to resist any breaking stresses towhich it might be subjected on account of the-tendency of the leading-in"wires to expand more rapidly than the lass.

Furthermore, the glass of the neck 0 the receptacle presents a largeradiating surface which will insure rapid cooling of the stems. Theeyelets also, present comparatively large cooling surfaces within theswitch. 3 Therefore the comparatively short stems are provided at bothends with cooling. means that will prevent them from becomingoverheated, in use, to such an extent as to injure the seal.

The electrodes? and 4 are each made of a piece of wire bent at themiddle to form an eye, the free ends being bent radially .from t e eyeand lying side by side to produce a double stem 10. Each leading-in wireabuts at its inner end against the ends of both members of thecorresponding stem.

'When the parts are assembled as heretofore explained, the joint 11between each double stem and its leading-in wire, lies some- I whatoutwardly of the inner edge of the flattened neck. It will be seen thatthe cur-' rent flowing through a leading-in wire di-- vides at the stemof the electrode, one-half flowin through one leg of the stem, and

. the ot er half flowing through the other leg. Therefore the tendencyof the stems to become heated is greatl reduced because the value of thecurrent owing through each leg of the stem is only one-half of the totalcurrent. I

In the arrangement shown in Figs. 5 and- 6, all of the parts are thesame as in the arrangement just' described excepting that instead ofmaking the electrodes in the form of eyelets, they take the shapeof'small discs.

13. Each disc has a stem 12, joined to the corresponding leading-inwire, as indicated at 14, a short distance outwardly from"the inner edgeof the flattened neck, The discs:-

provide a larger radiating surface for the dissipation of heat thatmaybecreated in the stems, than do the eyelets, but otherwise the principlesinvolved are the same in the construction shown in Figs. 5 and 6 as inthat illustrated in Figs. 1 and 2.

While wehave illustrated and described.

with particularity only a few forms of our I ing outwardly from one endthereof, leading-in wires extending through said neck and havingelectrodes extending into the chamber within said shell, said leading-inwires being spaced a considerable distance apart from each other in thedirection of the long transverse dimension of said neck, said electrodesbeing circular in shape, arranged adjacent said neck, and in arallelplanes extending at right angles to tli long dimension of said neck,thereby presenting comparative large cooling surfaces within the shellwhereby the temperature of the electrodes is reduced before they engagethe glass seal.v

2. device of the character described comprising a Sealed glass shellhaving a comparatively wide thlll-SOlld neck extending outwardly fromoneend thereof, lead- I ing-in wires extendingthrough said neck andhaving-electrodes extending intothe chamber within said shell, saidleading-in wires being spaced a considerable distance apart from eachother in the direction of the long transverse dimension of said neck,the electrodes being connected to the leading-in wires by joints encasedwithin the neck, the free ends of said electrodes being bent radially toform eyes adjacent said neck, said eyes arranged in parallel planesextending at right angles to the plane of the long dimension of saidneck, thereby presenting comparative large cooling surfaces within theshell whereby the temperature of the electrodes is reduced before theyengage the glass seal.

3. A device of the character described comprising a sealed glass shellhaving a wide thin solid neck extending outwardly from one end thereof,electrodes within said shell having comparatively thin stems, and leading-in wires attached to said stems, the stems of the electrodes beinspaced apart from each other in the direction of the long transversedimension of said neck, and the joints between the stems and theleading-in 0 plane of the electrodes being formed of wire bent at themiddle to form eyes with the free ends extending radially from the eyesand lying side by side to produce double stems abutting the respectiveleading-in wires, whereby currentflowing through a lead-in wire dividesat the double stem and reduces the tendency of the respective stems tobecome excessively heated-at the said joint. I

In testimony whereof, we sign this speci- 10 fication.

IRA E. MQCABE. RAYMOND W. ARMSTRONG.

